parse()
parse the stream, and create a MimeHeaderHolder containing all
the parsed headers, in lenient mode
Always be lenient by default (general rule is: be lenient in what you
accept conservative with what you generate).

parse(boolean lenient)
parse the stream, and create a MimeHeaderHolder containing all
the parsed headers, note that invalid headers will trigger an exception
in stirct mode, and will just be removed in lenient mode

parse

parse the stream, and create a MimeHeaderHolder containing all
the parsed headers, in lenient mode
Always be lenient by default (general rule is: be lenient in what you
accept conservative with what you generate).